Officials in Bangladesh are declaring three areas within the southern Sundarbans mangrove forest as dolphin sanctuaries.

The Ganges river dolphin is classified as Endangered on the IUCN Red List

Protecting freshwater dolphins

The Sundarbans mangrove forest, one of the largest forests of its kind, is an area of great biological diversity, housing hundreds of species including the majestic Bengal tiger and more than 260 bird species. Its waters are particularly important, being the only place in the world where threatened Ganges river dolphins and Irrawaddy dolphins can be found.

Tapan Kumar Dey, a senior wildlife conservation official, spoke about the creation of the three freshwater havens: “We have decided to declare Dhangmari, Chandpai and Dudhmukhi areas of eastern Sundarbans as dolphin sanctuaries so that these mammals can survive in a safe environment.”

Irrawaddy dolphin breaching

Identifying hotspots

The sites were identified as dolphin hotspots following a nine-day survey conducted by the Wildlife Conservation Society’s Bangladesh Cetacean Diversity Project (BCDP) in the western part of the Sundarbans mangrove forest earlier this month.

The waters of the Sundarbans play host not only to the endemic Irrawaddy and Ganges river dolphins, but also to other cetacean species including the finless porpoise and the Indo-Pacific humpback dolphin. These two species are normally found along the coast, but migrate upriver during the winter when salinity levels are high, only returning to coastal waters once fresh water begins flowing into the rivers.

Rubaiyat Mansur Mowgli, principal researcher of the BCDP, said: “This year we encountered many of them during the recent survey, soon after the rains when the salinity level is low. Their presence in this region at this time may be an indication of the rising salinity level.”

Adult female Indo-Pacific humpback dolphin with a calf

Risk factors

The impressive diversity of cetaceans found within the aquatic ecosystem of the Sundarbans is at risk from a variety of factors, including rising salinity levels and pollution. Fishing is another threat, as although dolphin species are not usually targeted by fishermen, the animals do still get entangled in fishing nets and drown.

Mr Dey hopes that the creation of the new dolphin sanctuaries will go someway to reducing death tolls as a result of accidental entanglement: “The waterways in these areas will be clearly demarcated and there will be signpostings so that local fishermen will not venture into this region for fishing.”

Irrawaddy dolphin swimming alongside a fishing boat

A step forwards

An official notice regarding the establishment of the sanctuaries is expected to be issued by the ministry of environment soon.

The creation of the protected areas is certainly a positive step towards safeguarding the future of the Sundarbans’ aquatic life, but Mr Mowgli warns that the battle to protect threatened species in the region is not yet over: “Declining freshwater supplies and rising sea levels due to global climate change are affecting the dolphin population.”

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